In a number of diseases, a pathological Th1 or an attenuated Th2 reaction has been causally demonstrated or these reactions are the subject of discussion. Findings from animal experiments give rise to the supposition that a change in immune response towards Th2 has a protective effect in these diseases. Organ-specific autoimmune diseases such as the following may be cited in this context: multiple sclerosis [Shevach, E. M. et al., Springer Semin. Immunopathol. 21 (1999) 249-262; Leonard, J. P. et al., Crit. Rev. Immunol. 17 (1997) 545-553], autoimmune uveitis [Singh, V. K. et al., Immunol. Res. 20 (1999) 147-161; Sun, B. et al., Int. Immunol. 11 (1999) 1307-1312; Egwuagu, C. E. et al., J. Immunol. 162 (1999) 510-517], insulin-dependent diabetes mellitus [Rabinovitch, A. et al., Biochem. Pharmacol. 55 (1998) 1139-1149; Cooke, A. et al., Parasite Immunol. 21 (1999) 169-176], rheumatoid arthritis [Muller, B. et al., Springer Semin. Immunopathol. 20 (1998) 181-196], Behçet's syndrome [Frassanito, M. A. et al., Arthritis Rheum. 42 (1999) 1967-1974] and furthermore Helicobacter pylori infection (the cause of, among other things, gastric ulcer and atrophic gastritis) [Smythies, L. E. et al., J. Immunol. 165 (2000) 1022-1029; Fox, J. G. et al., Nat. Med. 6 (2000) 536-542; Mattapallil, J. J. et al., Gastroenterology 118 (2000) 307-315], inflammatory intestinal diseases such as Crohn's disease and others [Romagnani, P. et al., Curr. Opin. Immunol. 9 (1997) 793-799; MacDonald, T. T., Curr. Top. Microbiol. Immunol. 236 (1999) 113-135], acute organ transplant rejection reaction [Morelli, A. E. et al., Transplantation 69 (2000) 2647-2657] and spontaneous recurrent abortions (Jenkins, C. et al., Fertil. Steril. 73 (2000) 1206-1208].
In relation to initiation of Th1 and Th2 response, cytokines are regarded as key factors [Paul, W. E. et al., Cell 76 (1994) 241-251], with IL-4 probably representing the decisive cytokine signal for the differentiation of naïve T-helper cells into T2 cells. The initiation of a Th1 response is on the other hand controlled essentially by IL-12 and IFN-γ, which are produced by dendritic cells and other accessory cells. Apart from cytokines, other factors may also influence T-cell differentiation [Constant, S. L. et al., Annu. Rev. Immunol. 15 (1997) 297-322]. For initiation, IL-4 or IL-12 must be present by the time of priming, i.e. early during an immune response (cf. FIG. 1).
The early production of IL-4 or IL-12 and thus T-cell differentiation are controlled by exogenous and endogenous factors. Among the exogenous factors, the nature of the pathogen is particularly important. A number of pathogens preferentially stimulate a Th1, others a Th2 response [Scott, P. et al., Immunol. Today 12 (1991) 346-348]. This gives rise to the supposition that molecular properties of the corresponding pathogen are responsible for the effect in question. As the nature of the pathogen decisively influences early cytokine production, the fundamental question arises as to what the molecular trigger factors are that induce early IL-4 or early IL-12, and what the cellular source is that provides these cytokines.
The cellular source for early IL-4 is the subject of controversy [Coffrnan, R. L. et al., J. Exp. Med. 185 (1997) 373-375]. In principle, several cell types are capable of producing IL-4 if appropriately stimulated: type 2 T cells, murine NK1.1+ T cells, eosinophils, mast cells and basophils. During a primary immune response, early IL-4 very probably originates from cells of the innate immunity, since mature antigen-specific T cells are not yet available at the time of first contact with an immunogen. Even in cases of pre-existing cross-reactive Th2 cells, the question remains as to what structure their development has produced. Type 2 T cells are therefore to be ruled out as the source of early IL-4. The postulated exclusive role of NK1.1+ T cells as the supplier of early IL-4 in the mouse has been called into question by experiments with genetically deficient animals [Coffman, R. L. et al., J. Exp. Med. 185 (1997) 373-375].
Various authors have suspected that basophils are involved in the development of a Th2 response [Paul, W. E. et al., Cell 76 (1994) 241-251; Romagnani, S., Immunol. Today 13 (1992) 379-381; Dahinden, C. A., Int. Arch. Allergy Immunol. 113 (1997) 134-137]. In support of this suspicion is the fact that human basophils release considerable quantities of IL-4 within a few hours following antigen-specific and non-specific stimulation [Brunner, T. et al., J. Exp. Med. 177 (1993) 605-611; Kasaian, M. T. et al., Int. Immunol. 8 (1996) 1287-1297]. In addition, basophils may, as mobile cells of peripheral blood, accumulate rapidly at sites of conflict with pathogens. Migration and accumulation are controlled by a number of chemokines. Eotaxin, which attracts basophils, eosinophils and Th2 cells by binding to their chemokine receptor CCR3, should be emphasised in particular. Interestingly, IL-4 leads to the release of eotaxin from human skin fibroblasts and endothelial cells, which probably represents an amplification mechanism for the recruitment of basophils. In addition to its chemotactic action, eotaxin clearly intensifies antigen-induced IL-4 release from basophils. Compared with basophils, IL-4 production by mast cells and eosinophils is low, which puts their role in Th2 induction into context. In summary, principally basophils are thus considered as producers of early Il4.
The question of the trigger factors for early IL-4 has to date not been definitely answered. For early IL-12, on the other hand, triggering factors are already known. Thus, for example, bacterial products such as lipopolysaccharide and CpG-oligodesoxynucleotides, may induce macrophages or dendritic cells to rapidly release IL-12 and bring about Th1 induction in vivo [Paul, W. E. et al., Cell 76 (1994) 241-251; Bohle, B. et al., Eur. J. Immunol. 29 (1999) 2344-2353]. The identification of factors for Th2 induction has still to be carried out. However, potential trigger factors that induce rapid IL-4 release from basophils in vitro have already been described: the B cell superantigens protein Fv [Patella, V. et al., J. Immunol. 161 (1998) 5647-5655] and HIV glycoprotein 120 [Patella., V et al., J. Immunol. 164 (2000) 589-595], which become active by binding to the VH3 segment of IgE, and lectins [Haas, H. et al., Eur. J. Immunol. 29 (1999) 918-927], which bind to the carbohydrate side chains of IgE or the IgE receptor.
For the therapy of certain diseases, it would be desirable to direct the immune response towards a type 2 T-helper cell response (Th2 response). There have to date not been satisfactory possibilities for this, and the administration of IL-4 as such is not practicable for routine use as it is too costly and expensive.
The object of the present invention is therefore to make available highly potent Th2 inducers and medicaments for immunomodulation.
This object is achieved according to the invention by new proteins that are isolated from parasitic worms.
Parasitic worms can essentially be classified into three major taxonomic groups of helminths (zestodes, trematodes and nematodes) and are characterised by a parasitic mode of living within vertebrates and/or invertebrates. There, they attack specific organs/tissues: the lumen of the bowels (intestinal nematodes), epithelia (lungworms), blood vessels (schistosomes), lymph vessels and skin (filariae) and various body tissues (larval stages of tapeworms) and are in this connection confronted with differing immunological conditions.
Worldwide, around 3.5 billion people are infected with parasitic worms. Even though direct mortality is low, those affected may experience considerable failure to grow, developmental and organ damage and often chronic disease.
The most important representatives of parasitic worms in humans: the intestinal large round worm (Ascaris lumbricoides; around 1 billion people infected), hookworms (Ankylostoma duodenale and Necator americanus; nearly 1 billion), whipworm (Trichuris trichiura; around 800 million), schistosomes (around 200 million), filariae (Brugia, Onchocerca and Wuchereria, around 100 million) and tapeworm species (Taenia; around 50 million).
In animals, infection with parasitic worms, of which there are very many different types, is far greater than in humans. The economic damage inflicted on farm animals can be substantial.
The invention is based on the finding that above all parasitic worms reliably induce a Th2 response. In this context, the property of Th2 induction may be limited to a specific stage of development. Thus, in the case of infection of mice with the trematode Schistosoma mansoni, the egg stage induces a Th2-type immune response, while the schistosomula (larval) stage induces a Th1-type immune response [Pearce, E. J. et al., J. Exp. Med. 173 (1991) 159-166]. The IL-4-inducing capacity of schistosome eggs is so pronounced that even naïve mice respond to the administration of schistosome eggs following a transient Th0 response within 7-10 days with a Th2 response and IgE synthesis [Vella, A. T. et al., J. Immunol. 148 (1992) 2283-2290]. Even after the intranasal administration of S. mansoni egg extract, systemic IgE production occurs in the mouse model [Okano, M. et al., J. Immunol. 163 (1999) 6712-6717]. It has so far not been achieved, however, to identify or isolate the active substances responsible for the pronounced IL-4-inducing capacity of S. mansoni eggs.